1. Field of the Invention
The following description relates to a zoom method of a small digital camera. More particularly, the following description relates to a small digital camera attached to a mobile communication terminal that automatically zooms according to a photographing mode, such as a portrait mode and a text mode.
2. Background of Related Art
A camera may provide a zooming function capable of enlarging/reducing an image of a subject based on a user's need. The zooming function may be divided into an optical zoom and a digital zoom. The optical zoom is for enlarging/reducing an image based on movement of a zoom lens back and forth. The digital zoom is for enlarging/reducing an image by calculating (and interpreting) a distance on a computer.
A general digital camera may not have a limitation of body size so that both the optical zoom and the digital zoom are adopted therein. The digital camera may automatically zoom according to a photographic mode.
In an automatic zoom process, various photographic modes (e.g., portrait, party, night view, close up, black and white, back light, scene, text, and etc.) may be provided in the digital camera, and an optimum exposure, a focus, a white balance, etc. may be automatically controlled according to photographic surroundings (or a subject). The portrait mode may be for photographing a natural portrait by closing up a figure and making voluminous in a clean background state. The back light mode may be for not generating a shadow of a figure at the time of photographing against the light. The text mode may be used for photographing letters or a simple text and storing these features.
In the automatic zoom process, the digital camera may automatically control a focus by using a through-the-lens (TTL) phase difference detection method, a contrast detection method, a sound wave detection measurement method, an infrared ray measurement method, etc.
The TTL phase difference detecting method is a method for measuring values of a subject through two optical devices (having different positions) and focalizing towards a direction that minimizes a difference of the values.
The contrast detecting method is a method for focalizing by comparing darkness between each image inputted through two range finders. The sound wave detection measurement method is for measuring a distance and controlling a focus by using the time for an ultra sound wave irradiated on a subject to return.
The infrared ray measurement method is for irradiating the infrared ray towards a subject and calculating a distance to the subject through an angle between a reflection light and an irradiation light of the subject and then controlling a focus by using a light source of an infrared ray irradiated on an infrared ray subject and an infrared ray reaction optical device that receives a reflection light reflected from the subject.
In order to implement the automatic focus controlling method, a distance measuring device is attached by hardware. However, a small digital camera attached to a mobile communication terminal has size limitations as compared to a general digital camera such that only a hand-operated digital zoom function may be provided for the small digital camera. That is, the small digital camera of a mobile communication terminal may provide a hand digital zoom function without any automatic focus controlling method as in general digital cameras and thereby the problems of the various photographic modes may not be automatically provided.
In small digital cameras of mobile communication terminals, it is difficult to implement an automatic focus controlling function according to a photographic mode using a hardware distance measuring device due to size limitations. Additionally, attaching the hardware distance measuring device to the small digital camera of the mobile communication terminal not only prevents a corresponding mobile communication terminal from becoming small but also increases the material cost.